X-ray apparatus



June 18, 1935. J. M. HOUIIMAN 2,005,035

X-RAY APPARATUS Filed May 22, 1933 Patented June 18, 1935 UNITED STATES X-RAY APPARATUS Jacobus Marinus Houtman, Eindhoven, Netherlands, assignor, by mesne assignments, to N. V. Philips Gloeilampenfabrieken, .Eindhoven, Netherlands, a Dutch company Application May 22, 1933,-Seria1No. 672,328

In Germany May 20, 1932 6 Claims. (o1. 250 34 The present invention relates to an X-ray or similar ray-emitting apparatus and more particularly to means and methods for sustaining such apparatus by magnetic force in operative relation with a body, for instance, with a metal plate, to be examined.

The examination of materials as to their thickness, flaws and proper welding by means of X-rays or other penetrative radiation, has gained considerable importance in recent years.

For this purpose the object to be examined, for instance a steel plate, is placed between the source of penetrative rays and a suitable ray-receiving means, for instance, a fluoroscopic screen or photographic film or plate, and its thickness, or the character of its Welds or the existence of flaws, and thus in general the strength of the object is determined.

For the determination of the thickness of a plate or of other structural members by means of X-rays or other radiant energy, a convenient method has been described in the copending application of Bouwers and Boldingh, Ser. No. 586,224, filed January 12, 1932, in which the distance between the shadow points of two markers is used to determine the thickness of the member.

As a rule, in the past when X-rays were used for such examination, the body to be examined had to be carried to a stationary X-ray apparatus and this not only entailed considerable work, but such examination of many structural parts, as for instance that of the walls of ship bodies or of the welds on steel beams of buildings was altogether unfeasible.

The invention described in the copending ap plication of Bouwers Ser. No. 178,457, filed March 25, v1927, now Patent No. 1,949,005, dated February 27, 1934, provides for a shockproof X-ray tube which can be conveniently rendered portable and brought into operative relation with any such structural body to be examined.

For instance, such a portable X-ray apparatus can be suitably used for the examination of the thickness of ship walls whereby according to the above referred to application of Bouwers and Boldingh,,two marks are provided on the wall portion the thickness of which is to be measured, and the X-ray tube is placed at a definite distance from the wall and a fluorescent screen or a photographic plate placed on the other. side of the wall, also at a definite distance therefrom, or directly against the wall portion to be examin d, and th dis an of h adowso h tural body. 7

A further object of the invention is to provide 13.

marks appearing on the screen orplate, used to determine the thickness of the plate.

In many instancesas for instance, when examining the thickness and strength of a= ship body or when examining a large number of welds,

a large number of examinations or measurements have to be made and in such cases it is of great importance to reduce the time consumed by and between the individual examinations.

In such cases it is among other things, impor .l tant that the tubebe so supported that it can be moved both horizontally and vertically so as to be brought in operative relation with any structural portion to be, examined.

For example when examining the wall of a ship :11

body this can be achieved, for instance by suspending the X-ray tube from the top by means of asuitable, lifting device. I

However, such suspension does not sufiice,,to

properly fix the X-ray tube inrelation to the 21 parts to be examined, and for instance, vibrations Even without interferingvibrations it is diifi- 2:

cult to maintain the proper distance betweenthe tube and the plate to be examined unless the tube is pressed against the wall by special means.

One objectof the present invention is to overcome all of the above difiiculties by providing for .3

means and methods which render possible by means of penetrative rays the rapid and accurate examination of the different portions of a strucfor means whereby an X-ray tube or other source of penetrative rays is suspended in operative re- .lation with the structural body to be examined by means of magnetic force.

A stillfurther object of the invention is to .4 suspend in operative relation with a body to be examined, an X-ray tube or other source of penetrative rays as well as a suitable receiver for such rays by means of the magnetic force obtained from a common magnetic flux.

A un further object of my invention is to vretain a source of penetrative rays and a rayreceiver on the opposite sides of a non-magnetic body to be examined, by means of magnetic force.

A still further object of the invention is'to pro- 15 vide an X-ray apparatus or other source of penetrative rays which is structurally combined with a permanent or electro-magnet serving to locate said source operative relation with the body to be examined. '5

A still further object of the invention is to so combine the source of penetrative rays and the magnet serving to locate the same in operative relation to the body to be examined, that the magnetic field of the magnet does not influence the rays generated in and/or emanating from said source. I

A still further object of the invention is to provide an electro-magnet for the suspension of the source of penetrative rays in operative relation with the body to be examined, the core of which has a comparatively high residual magnetism and which creates a sufiiciently large magnetic pull to firmly hold the devicein its position after the magnet has been pressed to the body by the passage through its coil of a current of small intensity and short duration; and'which magnet can be conveniently loosened by sending through the coil a small current of reversed direction.

A still further object of my invention is toprovide a magnet for the suspension of the source of penetrative rays, which is provided with interchangeable pole-shoes, the shapes of which conform with the surface of the body to be examined.

A still further object of my invention is an X- ray tube which is provided with a metal envelope which also serves as part of the yoke of the hold- .ing magnet.

A still further object of my invention is to provide for methods to accurately determine the position of the ray-receiver with respect to the source of penetrative rays.

A still further object of my invention is to provide for a limited relative movement between the X-ray tube and its holding magnet.

A still further object of my invention is to provide a separate auxiliary magnetic holding body which carries part of the Weight of the ray-penetrating source and of its holding magnet.

A still further object of my invention is to provide fora limited relative movement of the X-ray tube and its holding magnet with respect to the auxiliary magnetic holding body.

the ray-receiver, are magnetically held against the body to be examined. 7

It is well known to utilize the holding power of a magnet and in the U. S. Patent No. 1,712,889

'it has already been'proposed to use the magnetic force to fix a testing device in operative relation to an object to be examined.

However, in connection with devices the performance of which may be influenced by the strong magnetic field of the holding magnet, magnetic suspension has not been utilized so far and such arrangement would appear altogether unsuitable due to the danger of interference by T the magnetic field of the magnet.

Applicant succeeded in utilizing the holding force of a permanent or electro-magnet in connection with asource of penetrative rays, by providing a construction and means in which the magnetic field of the magnet in no way interferes with the rays emerging from the source.

I shall describe my inventionin connection with an X-ray tube serving as the source of penetrative rays, although as stated, other suitable sources,

for instance radium whichemits gamma rays may be used.

According to the invention the X-ray tube is magnetically held against the structural member.

to be examined. On the other side of said member is disposed and held, preferably also magnetically, the ray-receiver, for instance a fluorescent screen or a cassette provided with a photographic film or plate, the frame of the screen or the cassette being or having attached to it a magnetizable body. Preferably the same magnetic flux fixes both the X-ray tube and the receiver.

To obtain good results the X-ray tube and the receiver have to be pressed against the body to be examined, with great force. This requires high magnetic forces. On the other hand, for convenient and quick handling, it is necessary to easily loosen the magnetically-supported member.

For this reason electro-magnets are more suitable for such purpose than are permanent magnets. However, to create large magnetic forces 'electro-magnets usually require comparatively ism, is made of a material which has a comparatively high residual magnetism, for instance of a good magnet steel, such as the well known K. S. magnet (vide Handbook of the American Society for Steel Treating) containing in addition to iron cobalt, 0.6% carbon, 2% chromium and 7% tungsten.

A comparatively small magnetizing current of short duration creates a sumciently large magnetic pull to firmly press the magnet poles and the ray-receiver against the walls of the object to be examined and this current may be'then interrupted, whereby the force due to the residual magnetism of the magnet is sufiioient to firmly hold the X-ray tube and the ray-receiver in their proper position.

To loosen the apparatus from the wall of the object after the examination has taken place, a small current of reverse direction is sent through the magnet coils, which partly demagnetizes the magnet yoke so that the holding magnet and ray-receiver can be easily loosened.

The above arrangement has the important advantage that no current is required for holding the apparatus during examination and no special supporting means are required to safeguard the apparatus from dropping should the current be unintentionally interrupted.

The holding magnet for the X-ray apparatus may be of very simple construction. It may comprise one or more individual magnets of which one or more poles are placed directly against the surface of} the object to be examined.

The magnet should be capable of producing a strong magnetic field which firmlypresses the poles against the object to be examined, and also provides for a sufiicient flux to magnetically hold the ray-receiver against the opposite side of the object.

In case the body examined is of ferro-magnetic material, the magnetizable portion of the ray-receiver is magnetized by the stray flux created on the receiver side of the body, respectively by the stray flux of this body which due to the induced magnetism also acts as a magnet.

In case the body to be examined is of non -magnetizable material the magnetizable portion of the ray-receiver completes the magnetic circuit of the holding magnet. 1

It is not altogether necessary that the holding power of the magnet be sufficient to carry its own weight and that of the X-ray tube, and the strength of the magnet may be limited to the pull required to intimately press it, as .Well as the ray-receiver against the walls of the body to be examined, and auxiliary suspension means may be provided which fully or partly carry the weight of the apparatus. For instance, the 'apparatus may be suspended from the top to a chain which in turn is carried by a suitable hoisting device. Instead of, or in addition to such chain uspensio n aux liary hol i m n y be provided, which may be a permanent magnet or an electro-magnet and to which the X-ray tube and its holding magnet are connected, preferably by articulated connecting means.

Preferably provisions are made for a limited freedomof movement of the X-ray tube and its holding magnet, with respect to the auxiliary magnet.

Preferably all of the parts including the X-ray tube and the connecting cables are surrounded by metallic envelopes which are at ground potential and thus render the whole apparatus shock-proof;

Both the operating current for the X-ray tube and the magnetizing current may be obtained from the regular alternating network in a simple manner, the X-ray tube being connected through a transformer to said source and the direct current for the magnet may be obtained by rectifying the alternating current through a rectifier device, using preferably hot cathode gasfilled rectifier tubes.

As the surfaces of the structural bodies to be examined may have diiferent profiles and as 'an intimate contact of the magnet poles with these surfaces is imperative, it is preferable to provide the magnet yoke with pole-shoes which have differently shaped end surfaces and which are easily interchangeable.

The exact position of the ray-receiver with respect to the source of penetrative rays can be conveniently determined, by determining on the receiver side the points of maximum magnetic field strength, either by determining the position of maximum magnetic pull or by means of magnetic needles which are preferably directly secured to the ray-receiver.

While, as stated, I have illustrated my invention in connection with an X-ray tube serving as the source of penetrative rays, it can be applied to other sources of penetrative rays and the rayreceiver may not only be a photographic plate or a fluorescent screen but any other type of device, for instance, an ionization chamber, which is adapted to detect or record the rays penetrating through the examined body.

My novel apparatus and methods have a wide field of application in the examination of structural members to determine their thickness, the existence of flaws, the quality of welds, etc. They are excellently suitable for the examination of extended structures as ship bodies, bridges or buildings, etc., and irrespective of whether or not the structural member'to be examined is of magnetizable or non-magnetizable material.

The invention will be more clearly understood by reference to the accompanying drawing, which represents diagrammatically by way of example, devices for carrying out the new methods and forms of construction of the apparatus according to the invention.

Figure 1 is a front View of an X-ray tube provided with magnetic holding means showing the apparatus held in operative position for the examination of a plate.

Fig. 2 is a side view partly in section of the apparatus of Fig. 1 also showingv the ray receiver positioned on the other side of the plate.

Fig. 3 is a view of the apparatus of Figs. 1 and 2,

as seen from the side of the ray-receiver.

Fig. 4 is a front view of a modified construction of my invention, in which a metal envelope surrounding the X-ray tube forms part of the magnet-yoke.

Fig. 5 is an end view of Fig. 4.

Fig. 6 is a detail of the yoke end and of one shape of interchangeable pole shoe,

Fig. 6a shows another shape of pole shoe.

Fig. 7 is a side view of another modification of my invention in which an auxiliary magnetic carrier is provided to carry part of the weight of the X-ray tube and its supporting magnet, and in regard to which the tube can be displaced to a limited extent.

Fig. 8 is an end view, partly in cross-section, of an apparatus according to my invention, for measuring the thickness of a plate.

Referring to Figs. 1 to 3, the'X-ray tube l is preferably constructed along the general principles set forth in the above-referred to Bouwers patent, and is surrounded by a metal envelope and provided close to its two ends with two carriers, each carrier consisting of a clasp 3 which surrounds the tube andwhich is attached to a U- shaped yoke 4.

The'upper leg of each yoke 4 is secured to the ends of a chain 2 which is carried by suitable hoisting means.

Each leg of the yoke 4 is surrounded by a coil 5 and terminates in suitable pole-shoes 6, which are brought into contact with the object to be examined, for instance, with a. steel plate '1 forming part of the wall of a ship body.

The X-ray tube is provided with a ray-emitting window from which extends a conical applicator T 8. When an electric current is passed through themagnet coils the pole-shoes are tightly pressed against the plate and firmly adhere thereto, thus -fixing the X-ray tube with respectto the wall.

A suitable ray-receiver 9, for instance, a fluorescent screen or a cassette containing a film or plate, .is disposed on the other side of the wall Iv and is provided at its two ends with U-shaped bars 10, which are traversed by the stray field of the magnet extending to the other side of the wall, Instead of providing separate yokes H), the photographic cassette or theframe of the screen may form the magnetizable yoke.

It should be noted that my apparatus can also be used for the examination of bodies which are of non-magnetizable material, in which case the magnetic circuit of the electromagnet is completed through the yoke ill and the mutual attraction of the poles 6 and yoke l8 firmly fixes the a receiver.

wires (not shown) X-ray tube and the ray-receiver in the proper position.

The electric current for the X-ray tube is supplied through suitable flexible cables l6, which may be surrounded by a flexible metal tubing,

which mechanically protects the cable and which is preferably electrically connected to the metal envelope of the tube and is grounded. This renders the whole apparatus shockproof.

The cables it lead from the tube to the source supplying the electric energy for the X-ray tube, for instance, to the secondary winding of a transformer, the primary winding of which is connected to the regular alternating current network. The cables iii, are preferably of sufiicient length to permit the examination with the X- vray tube of the various portions of a body of extended surface without requiring the transformer to be moved.

The magnetizing current for the coils 5 is supplied from a suitable D. C. source through flexible This current source may be a rectified current obtained from the alternating network through a proper rectifier device, for instance, gas-filled hot-cathode rectifier tubes.

The yoke 41 is preferably of a material which has comparatively high residual magnetism. In using such a yoke material, a comparatively small magnetizing current suffices and this current needs only to be applied for a short time, to firmly position the magnet. Once the magnet has been thus pressed against the object to be examined, the magnetizing current may be interrupted, as the residual magnetism of the yoke is 'sufiicient tofirmly retain the magnet with the II-ray tube as well as the ray-receiver in their instance, in the examination of an extended surface, when the mutual position of the tube and receiver cannot be precisely ascertained by direct observation, one of the two following methods may be used:

The Y ray tube with its magnet having been brought into the desired position with regard to the object to be examined, the ray-receiver is held against the opposite side of the object so as to approximately oppose the X-ray tube, re-

spectively, the magnet. The ray-receiver is thereupon shifted about, until the position is found in which it is most strongly attracted by the magnet and which is the proper position of the ray- This position of maximum magnetic pull is quite pronounced and can be easily determined, especially if the end poles of the yoke of the ray-receiver are so designed as to form a direct continuation of the poles B of the yoke 4.

Another method of ascertaining the exact location for the ray-receiver, is by means of one or more small magnetic needles or compasses which are preferably mounted on the ray-receiver. Such a composs needle 22, as shown in Fig. 4 points perpendicularly to the wall to be examined when it is in exact opposition with one of the pole pieces 6 of the yoke 4, whereas halfway between the pole pieces it assumes a position parallel to thewall, and in intermediate position assumes intermediate angular positions. Preferably the compass or compasses are secured to the yoke or clamping pieces 0 of the ray-receiver.

Instead of magnetic needles, iron filings may be used in a similar manner; however, such filings have the drawback that they adhere to the emerging through the window. and confined by v the applicator 8, pass the wall I, and impinge on the ray-receiver 9.

To loosen the magnet a small current of reverse direction is sent through the coils 5, which partly demagnetizes the yoke and permits the easy loosening of the magnet and of the ray-receiver, and these can now be conveniently brought into operative position for the examination of another portion of the body.

As the cathode rays produced in the discharge space of the X-ray tubes, which in their turn produce the X-rays, are subject to be influenced by a magnetic field, and as the holding magnet produces a strong magnetic field, care has to be taken to prevent the magnetic flux of the magnet from interfering with the direction of the cathode ray beam.

Preferably the relative arrangement of the magnet and the X-ray tube should be such, that the cathode ray beam, or in other Words the discharge path of the X-ray tube, should fall within a space which is not traversed by the magnetic field, or if such arrangement is not altogether feasible, provision shouldbe made that the magnetic lines which pass through the tube have the same general direction as the cathode ray beam or are directly opposite thereto.v By such arrangement the electrons of the cathode beam remain substantially unaffected by the field of the magnet.

In order to permit a limited displacement of the X-ray tube without requiring the removal of the whole device, the X-ray tube may be arranged with regard to the magnet in such a manner that it can be slightly moved with respect to one or both magnet poles.

Figs. 4 and 5 show a different. embodiment of my invention in which a single magnet is provided instead of the two magnets of the construction of Figs. 1 to 3. Each leg of the magnet-yoke carries a coil H and I2, the two legs being interconnected by a metal envelope l5 of magnetizable material surrounding the X-ray tube proper, which envelope thus may have both the functions of shockproofing and mechanically protecting the tube, and also of forming part of the magnetyoke.

In this case the magnetic lines in the yoke 15 have the same direction as the cathode rays or a direction opposite thereto. If desired the cathode beam can be further screened from stray rays byproviding an inner screen of magnetizable material.

In Fig. 4 the apparatus is shown as used for the examination of welds between a curved profiled iron bar i3 and a curve plate It. To provide intimate contact between the magnet poles and the body to be examined, the shape of the pole pieces has to closely conform to the surface of the body. For this purpose it is preferably to provide interchangeable pole shoes having differently'shaped end-faces such as 18 or. l8, shown in Figs. 6 and 6a. This can be accomplished by providing the ends of the yoke legs ll with a cylindrical recess l9, into which snugly fits the stud 20 or 20 of differently shaped pole-shoes. I8 or I8.

It is not necessary that the magnet connected with the X-ray tube provide for sufficient pull to carry its own weight and also the weight of the X-ray tube, and as shown in Fig. 7, an auxiliary supporting body 25 may be provided, which may be a permanent magnet or an electromagnet and which carries part of the weight of the apparatus.

The body 25 is connected with the yoke Z l of tube 23 by means of an articulated bar 21. To permit some freedom of movement of the X-ray tub-e relative to the body 35, the end joint 26 of the bar 21 is connected to a slide 26, which can be displaced in a vertical direction with regard to the body 25. Such displacement can be obtained for instance, by the aid of a screw-spindle 29 operated by a hand-wheel 23. To also provide for the X-ray tube similarly freedom of movement in the horizontal direction the joint 25 may be formed as a ball and socket joint.

In Fig. 8 an arrangement according to my invention is shown for the measuring of the thickness of a body, for instance, that of a steel plate 33, by utilizing the method described in the above-referred to Bouwers and Boldingh application.

An X-ray tube Ed is demountably connected to a magnetizable yoke 32, for instance, by means of screws 39 39, which secure an extension of the metal envelope of the tube to the yoke.

Suitably connected to th yoke $52, for instance, by means of screws, are two cylindrical pole pieces Mi, each being surrounded by a coil. 3 i The coils 3i are surrounded by a housing Cit of non-magnetizable material, for instance of copper, to which is secured a cross-bar 35. Elastically connected with the crossbar 35, for instance, by the interposition of a coil-spring 4|, is a block 36 of nonmagnetizable material, for example of copper, having an end-plate t? which is flush with the end-faces of the poles iii, and which carries two markers 3i and 33. The markers 31 and 38 may be, for instance, tungsten wires which are not translucent to the X-rays.

Those rays of the X-ray tube which are intercepted by the markers, (one ray being indicated by the dot and dash line) form shadow pictures on a suitable screen disposed on the other side of the plate (not shown), and the distance between the shadow pictures of the markers 31 and 38 determines the thickness of the plate 33 in a manner fully described in the above-referred to application of Bouwers and Boldingh.

While I have described my invention in connection with specific embodiments and applications, I do not wish to be limited to such embodiments and applications, but desire the appended claims to be construed as broadly as permissible in View of the prior art.

Vifnat I claim is:

1. A device for examining a body by means of penetrative rays, comprising a source of penetrative rays and a magnet associated with said source, a receiver for said rays and a magnetizable member for said receiver, said magnet being adapted to hold said source in fixed relation with said body on one side thereof and to hold said rayreceiver on the opposite side of said body.

2. A device for examining a non-magnetizable body by means of penetrative rays, comprising a source of penetrative rays, a magnet associated with said source and a ray-receiver having a magnetizable member, said magnet being adapted to be positioned on one side of said body and having an open magnetic circuit, said ray-receiver when positioned on the other side of said body in proper relation to said magnet, completing through said member said magnetic circuit, the magnetic force exerted between said magnet and said member retaining said magnet, said source and said receiver in operative relation with regard to said body.

3. A device for examining a body by means of penetrative rays, comprising a source of penetrative rays positioned on one side of said body, a term-magnetic member connected to said source, a ray-receiver adapted to be positioned on the other side of said body and to oppose said source, and a ferro-magnetic member connected to said ray-receiver, a magnet coil to magnetize one of said ferro-magnetic members and to thereby create a magnetic force, said source and receiver being fixed against said body by means of said magnetic force.

4. A device for examining a body by means of penetrative rays, comprising two devices, one a source of penetrative rays and the other a ray receiver, a holding magnet associated with one of said devices, and a magnetizable member associated with the other of said devices whereby said source and receiver may be held by magnetic force in fixed relation on opposite sides of said body, said magnet comprising a yoke of a' magnetizable material having high residual magnetism and a magnetizing coil, said magnet upon passage of a small current or" short duration through said coil being adapted to firmly adhere against the body and to remain suspended to it by the residual magnetism of its yoke.

5. A device for examining a body by means of penetrative rays, comprising a source of penetrative rays and a magnet associated with said source, a receiver for said rays and a magnetizable member for said receiver, said magnet comprising a magnetizable yoke, said yoke being of a material having high residual magnetism, a magnetizing coil on said yoke and means to energize said coil, said yoke and said member being held by residual magnetism after said energizing means is disconnected, whereby said source can be held in fixed relation with said body on one side thereof and said receiver can be held on the opposite side of said body.

6. A device for examining a body by means of penetrative rays, comprising a part includinga source of penetrative rays adapted to be positioned on one side of said body, and a second part including a ray-receiver adapted to be positioned on the otherside of said body and to oppose said sourcc, one of said parts including a magnet and the other part incliding a magnetizable member, said magnet and magnetizable member being adapted to hold said sourceand said receiver in fixed relation on opposite sides of said body.

JACOBUS MARINUS HOUTMAN. 

